While neither a full nor a particularly sophisticated treatment of the issue of church/state separation, this is a compelling rebuttal to those who claim that America is a Christian nation. The authors don't address the many recent judicial controversies about public expression of religion. Instead, they explore the Constitution's origins and its ``intentionally secular base.'' They point out that even the religious men among those who ratified the Constitution wanted to distance religion from government. Also, they discuss the views of Roger Williams, who wanted to keep the church pure and thus separate; of John Locke, whose liberalism limited the role of the state; and of Thomas Jefferson, who incorporated Locke's ideas in America. Indeed, the authors note that the godless Constitutional structure was undermined only later, when God entered U.S. currency, in 1863, and in such institutions as the Pledge of Allegiance. The authors believe that while the Constitution does not exclude religion from the public square, it offers no special privileges; thus, they say, religious faith should not be a litmus test for political leaders. Kramnick teaches government at Cornell University; Moore teaches history there. (Jan.)